Criteria for auxiliary verbs

Can’t

• Negative contraction

  
  

• Emphatic positive

  
  

• Operator in reduced clause

  
  

• Independence of subject

They can all come

They all can come

• Negative contraction

• Emphatic positive

• Operator in reduced clause

• Postposition of quantifier

Can we go?

• Operator in negation

• Negative contraction

  
  

• Operator in inversion

• Emphatic positive

  
  

"Ann can do it"

• Emphatic positive

• Operator in inversion

• Operator in negation

• Independence of subject

I can come if you can

• Postposition of quantifier

• Operator in reduced clause

• Operator in inversion

• Negative contraction